The identification of gene mutations causing disease lends new insight into the pathogenesis and etiology of the disorder under examination. In collaboration with NINDS and NHGRI we are performing a whole genome scan and high density autozygosity mapping of families with a variety of neurological diseases. [unreadable] We have identified a region of linkage within chromosome 4 in a large in-bred PD family, a region containing a segregating haplotype on chromosome 3 in a blepharospasm family and a segregating haplotype on chromosome 17 in the dystonia family. We have identified genetic lesions at the ITPR1 locus underlying spinocerebellar ataxia (SCA) 15; mutations at TTBK2 as the cause of SCA11; genomic duplication as the cause of SCA20 and novel mutations in a stress reponse gene as the cause of a young onset dystonia parkinonism.